For the maintenance of refrigeration units, such as air condition systems or freezing systems, a maintenance technician uses various maintenance machines, each of which he has to transport to the respective site of use. Generally, the maintenance machines are transported along in a vehicle and have to be unloaded at the site of use and may have to be carried to the site of use over stairs and for longer distances. The maintenance machines include a refrigerant recovery machine (RRM) and a vacuum pump (VP). These maintenance machines are used independently and at different times. Each maintenance machine is rather heavy (12-14 kg) and has the size of a small suitcase. The refrigerant recovery machine further comprises a storage tank and scales. If a maintenance technician wants to seal a leak in a refrigerant circuit, the circuit has to be emptied first. In this context, environment protection regulations require that the refrigerant removed from the system is collected and that any refrigerant vapor is led into a refrigerant recovery tank together with the refrigerant. For this purpose, the maintenance machine is provided with a compressor that compresses the discharged refrigerant and pumps it into a storage tank.
Another type of maintenance machine comprises a vacuum pump driven by a motor of its own. The vacuum pump is used to draw air and water vapor from the pipe system of the refrigeration unit after the refrigerant has been drained before. Humidity and refrigerant do not go along with each other. The vacuum pump serves to dry the pipe system. For this purpose, a specific vacuum must be maintained for a certain time.
U.S. Pat. No. 5,606,862 and U.S. Pat. No. 5,678,415 each describe a maintenance machine. The maintenance machine has a motor with two shafts, one of which is adapted to drive a compressor via a first clutch and the second shaft is adapted to drive a vacuum pump via a second clutch. Shifting the clutches requires control operations.